b. Reliability of the Test
In this test of reliability, the writer used the split-half method that divided the number of the test become into two groups: odd and even.
The formula which was used: =
Notes: r
: coefficient or reliability between first and second half group x
: total number of the first half group y
: total number of the second half group x
2
: the square of the X y
2
: the square of the Y Lado in Hughes, 1991:3
After that, the researcher continuedthe calculation by using formula of Spearman Brown Hatch and Farhady, 1982: 268:
= +
Note: rk
: the reliability of the test rl
: the reliability of the half test
The criteria of reliability: 0, 90
– 1, 00 : high
0, 50 – 0, 89
: moderate 0, 00
– 0, 49 : low
3.6.2 Validity
A test can be said to be valid if it measures the object to be measured and suitable for the criteria Hatch and Farhady, 1982:250. It means that the test or instrument
which is used in the research can be said valid if the instrument measures the object to be measured and suitable with the criteria which is used in the research.
Setiyadi 2006:22 states that the instruments or tests are not valid if the instruments do not measure the object to be measured. He said that in the research
of the foreign language learning, there are four types of validity of instruments or
tests: face validity, predictive validity, content validity, and construct validity.
The face validity focuses on the layout or appearance of the test. Predictive validity is interrelated with the prediction the phenomena that will happen. For
this research, the writer used content validity and construct validity to measure the validity of the instruments or tests were good or not. The two types that were used
in this research are:
a. Content Validity
This validity concerns with the content details of the instruments. This validity analysis analyzes all the content of the instruments or tests whether the content of
the instruments represents the material that would be measured by the instruments. The content of the test was presented by the table below:
Table 2. Table of specification
No Objectives
Item Numbers Total Items
Percentage
1 Identify the main idea
1, 8, 16, 20, 28 5
17 2
Inference 2, 12, 13, 18, 27, 29, 30
7 23
3 Reference
6, 11, 14, 23 4
13 4
Specific information 3, 4, 9, 10, 17, 21, 24, 25, 26
9 30
5 Vocabulary
5, 7, 15, 19, 22 5
17
Total 30
100
b. Construct Validity
This validity was used to the instruments which have some indicator to measure one aspect. The construct validity of the instruments are measured by evaluating
the content whether all the content of the instrument concern to one aspect or not.
3.6.3 Level of Difficulties
The writer used the following formula to see the level of difficulty of the tests. It was calculated by the following formula:
�� = �
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